Apparatus for investigating fast chemical reactions by optical detection

An apparatus for investigating the course of fast chemical reactions by optical detection, said reactions being initiated in a chemical system under investigation by an external perturbation,

• said apparatus comprising a first light path for conveying a probing light beam, said first light path comprising a light source, means for monochromatic light filtering, collimating and focusing elements, a beam divider to provide a reference beam and a probing beam, and at least one photodetector, said apparatus further comprising a second light path for conveying a sensing light beam, said second light path intersecting said first light path within a region of intersection, said probing light beam being focused onto said region of intersection, said apparatus further comprising means for supporting a sample cell at said region, said sample cell forming a chamber for holding a liquid sample of said chemical system,
• said sample cell having two opposite windows and at least one further window, said windows having plane inner surfaces, said two opposite windows being transversed by said first light path and said further window being transversed by said second light path and the cross section of said chamber acting nearly completely as said region of intersection;
• said further window having a convexly curved outer surface forming a collecting lens, and the cross sectional area of said further window tapering from said lens surface towards said chamber;
• a further lens element close to said further window positioned in said second light path wherein said further window has a considerably larger aperture angle and a larger refractive power for light rays passing through the center of said chamber as compared to said opposite windows in said first light path, said second light path further comprising at least one photodetector, and means for spectral light filtering of the light in the second light path.